Non-destructive treatment process with uniform coverage

ABSTRACT

A non-destructive method of treating a nonwoven web resulting in uniform coverage throughout the web. The method includes saturating the nonwoven web in a treatment bath including at least one surfactant in an aqueous solution at a concentration between about 0.2% and about 8%, using one or more vacuums to extract excess bath from the nonwoven web, and using a dryer to evaporate water from the web. Add-on level of the treatment can be controlled through the vacuum air velocity, treatment concentration, and line speed. The invention further includes apparatus for carrying out the non-destructive treatment method.

BACKGROUND OF THE INVENTION

[0001] This invention is directed to a method of treating nonwoven webswithout destroying the fibers or the structure of the web whileproviding uniform coverage of the treatment throughout the web, andapparatus for carrying out the method.

[0002] Polymeric nonwoven materials are typically hydrophobic. Nonwovenmaterials are often used to make various components of a number ofdisposable absorbent products. Certain components, such as diaper surgemanagement layers and absorbent wipes, require nonwoven fibers to behydrophilic in order for the material to deliver its intended function.A number of topical treatment processes are available to make thesurface of the fibers hydrophilic. Such processes include spraying,foaming, and/or solution bath. In each of these treatment processes, thechemicals used to treat the fibers work by lowering the contact angle ofthe polymer surface, thereby rendering the fibers hydrophilic.

[0003] One type of topical treatment process uses a WEKO Rotor DampeningSystem, available from Weko, Biel AG, Switzerland. The general WEKOconfiguration is a centrifugal dampening application system using asingle or double rotocarrier. The surfactant formulation is pumped tothe WEKO header through a gear pump where it is fed to the dampeningrotors through restrictor tubes. Under the effect of a centrifugal forcegenerated by the spinning rotors, the chemical is dispensed to thenonwoven fabric in the form of small droplets. However, the WEKOprocess, as well as other spraying processes, lacks the capability touniformly treat nonwoven materials having high bulk and high basisweight and instead creates a gradient or laminar effect. Thus, theprocess results in inconsistent coverage. Furthermore, the process istypically quite messy.

[0004] Another type of topical treatment process is a foaming process.Even when applied to both sides of a substrate, the foaming processresults in inconsistent coverage of high bulk and high basis weightmaterials because the treatment is not uniformly applied and does notpenetrate into the web. Furthermore, the foaming process also requiresthe additional expense and hassle of a foaming agent.

[0005] Internal treatment of nonwoven fibers is also commonly used totreat nonwoven webs, wherein the treatment is injected directly into theextruder barrel of a fiber-forming process. While the process is cleanand easy to carry out, the treatment itself tends to burn off duringprocessing such that fibers are treated with only a fraction of atargeted add-on level making it difficult to determine the exact finaltreatment level. In addition, internal treatment can hinder the abilityto process or spin the fibers.

[0006] Yet another type of topical treatment process is a dip andsqueeze process. The dip and squeeze process saturates the web in asolution bath and uses nip rolls to squeeze the excess bath from theweb. While this process produces uniform coverage and sufficient webpenetration, when using high bulk materials the nips compress and shearthe web causing a loss in bulk. Thus, the dip and squeeze process is adestructive treatment process that changes the material properties, suchas bulk, density, bonding, and permeability. These changes have beenshown to negatively affect product performance in, for example,applications such as diaper surge management layers. Furthermore, thedip and squeeze method is limited to low bath concentrations because thenip cannot remove the bath efficiently. In addition to beingdestructive, the add-on level of treatment cannot be controlled in thismethod without affecting the material's thickness.

[0007] There is a need or desire for a method of treating nonwoven webs,particularly high bulk and high basis weight webs, that provides uniformcoverage and treatment penetration throughout the web and can be carriedout without destroying the bulk of the web. There is also a need ordesire for a non-destructive method of uniformly treating nonwoven websin which the percent add-on level of the treatment can be controlled.

[0008] There is a further need or desire for an apparatus to uniformlytreat nonwoven webs without destroying the bulk of the web, and havingthe ability to control the percent add-on level of the treatment.

SUMMARY OF THE INVENTION

[0009] In response to the discussed difficulties and problemsencountered in the prior art, a non-destructive method of uniformlytreating a nonwoven web, and apparatus for carrying out the method, hasbeen discovered.

[0010] The method of the invention can be used to treat high bulk andhigh basis weight nonwoven materials with uniform coverage and treatmentpenetration throughout the web, without destroying the bulk of the web.The method includes saturating a nonwoven web in a treatment bath ofknown concentration, using one or more vacuums to extract excess bath,and using a dryer to evaporate water from the web. A target add-on levelof the treatment can be achieved by balancing solution concentration,line speed, and vacuum air velocity. Suitably, the add-on level isbetween about 0.5% and about 4% weight by solids.

[0011] Unlike spraying and foaming applications, saturation in atreatment bath provides uniform treatment throughout the web. Thetreatment bath may include one or more surfactants in an aqueoussolution. The concentration of the surfactant(s) in the aqueous solutionis suitably between about 0.2% and about 8%, or between about 0.5% andabout 4%, depending on the final add-on level desired. The treatmentbath may also include a dye, such as a fluorescent brightener. To assurethe desired add-on level, the weight of the treated sample could doublethe dry weight. In other words, the nonwoven web could have about 100%wet pick-up of the treatment bath. Alternatively, the nonwoven web couldhave between about 25% and about 300% wet pick-up, depending on thenonwoven density, fiber size, fiber cross-sectional shape, and desiredtreatment level.

[0012] The line speed at which the nonwoven web is transported from thetreatment bath to the vacuum or vacuums, and to the dryer may be any ofa wide range of line speeds. For example, the line speed may be betweenabout 50 and about 200 feet per minute, or up to about 2000 feet perminute, or even faster. The vacuum or vacuums may have an air velocitybetween about 100 and about 3000 feet per minute. One or more vacuumsmay be used in the method. Rotary valves can be added to the vacuum orvacuums such that zone treatment may be created in the machinedirection, cross direction, or a combination of both directions. Thedryer may be set at a temperature between about 200 and about 250degrees Fahrenheit. After drying the web, the web may be wound onto aspool for storage.

[0013] Unlike processes that use nip rolls to squeeze excess bath fromthe web, the use of a vacuum to extract the excess bath from the web hasnot shown any decrease in bulk. In fact, the bulk has actually increasedin some cases as a result of undergoing the vacuum and subsequentheating and evaporation in a dryer. By using one or more vacuums inplace of nip rolls, material can be passed through the excess bathremoval area without undergoing any contact between two surfaces. Thisaids in reducing the compressive and shearing forces the web would facewith nip rolls.

[0014] The method of the invention is particularly suitable for use withhigh loft, high basis weight nonwoven webs. Such webs suitably have athickness of at least 0.08 inches, or between about 0.1 and about 1.5inches, with a basis weight between about 34 and about 500 grams persquare meter. The nonwoven web suitably has a density of less than about0.08 grams per cubic centimeter (g/cc), or less than about 0.06 g/cc, orless than about 0.04 g/cc.

[0015] Apparatus for carrying out the method of the invention suitablyincludes the treatment bath having a concentration between about 0.2%and about 8%, one or more vacuums, a dryer, and a device fortransporting the nonwoven web from the treatment bath to the vacuum(s)to the dryer.

[0016] With the foregoing in mind, particular embodiments of theinvention provide a method and apparatus for uniformly treating nonwovenwebs without destroying bulk.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is an illustration of an exemplary process for carrying outa dip and vacuum treatment according to one embodiment of the invention.

[0018]FIG. 2 is a photograph of a nonwoven web treated using thetreatment process of the invention with a solution including afluorescent dye, taken under black light.

[0019]FIGS. 3a & 3 b are photographs of a nonwoven web treated using aWEKO process with a solution including a fluorescent dye, taken underblack light.

[0020]FIGS. 4a & 4 b are photographs of a nonwoven web treated using afoam process with a solution including a fluorescent dye, taken underblack light.

[0021]FIG. 5 is a graph showing comparative FIFE test results ofnonwoven webs treated with different treatment processes.

[0022]FIG. 6 is a graph showing comparative LISTER test results ofnonwoven webs treated with different treatment processes.

DEFINITIONS

[0023] Within the context of this specification, each term or phrasebelow will include the following meaning or meanings.

[0024] “Hydrophilic” describes fibers or the surfaces of fibers that arewetted by the aqueous liquids in contact with the fibers. The degree ofwetting of the materials can, in turn, be described in terms of thecontact angles and the surface tensions of the liquids and materialsinvolved. Equipment and techniques suitable for measuring thewettability of particular fiber materials or blends of fiber materialscan be provided by a Cahn SFA-222 Surface Force Analyzer System, or asubstantially equivalent system. When measured with this system, fibershaving contact angles less than 90° are designated “wettable” orhydrophilic, while fibers having contact angles greater than 90° aredesignated “nonwettable” or hydrophobic.

[0025] “Machine direction” as applied to a film or web, refers to thedirection on the film or web that was parallel to the direction oftravel of the film or web as it left the extrusion or forming apparatus,or as it travels through a treatment process. If the film or web passedbetween nip rollers or chill rollers, for instance, the machinedirection is the direction on the film or web that was parallel to thesurface movement of the rollers when in contact with the film or web.“Cross direction” refers to the direction perpendicular to the machinedirection. Dimensions measured in the cross direction are referred to as“width” dimensions, while dimensions measured in the machine directionare referred to as “length” dimensions.

[0026] “Meltblown fiber” means fibers formed by extruding a moltenthermoplastic material through a plurality of fine, usually circular,die capillaries as molten threads or filaments into converging highvelocity heated gas (e.g., air) streams which attenuate the filaments ofmolten thermoplastic material to reduce their diameter, which may be tomicrofiber diameter. Thereafter, the meltblown fibers are carried by thehigh velocity gas stream and are deposited on a collecting surface toform a web of randomly dispersed meltblown fibers. Such a process isdisclosed for example, in U.S. Pat. No. 3,849,241 to Butin et al.Meltblown fibers are microfibers which may be continuous ordiscontinuous, are generally smaller than about 0.6 denier, and aregenerally self bonding when deposited onto a collecting surface.Meltblown fibers used in the present invention are preferablysubstantially continuous in length. “Nonwoven” or “nonwoven web” refersto materials and webs of material having a structure of individualfibers or filaments which are interlaid, but not in an identifiablemanner as in a knitted fabric. The terms “fiber” and “filament” are usedinterchangeably. Nonwoven fabrics or webs have been formed from manyprocesses such as, for example, meltblowing processes, spunbondingprocesses, air laying processes, and bonded carded web processes. Thebasis weight of nonwoven fabrics is usually expressed in ounces ofmaterial per square yard (osy) or grams per square meter (gsm) and thefiber diameters are usually expressed in microns. (Note that to convertfrom osy to gsm, multiply osy by 33.91.)

[0027] “Polymers” include, but are not limited to, homopolymers,copolymers, such as for example, block, graft, random and alternatingcopolymers, terpolymers, etc. and blends and modifications thereof.Furthermore, unless otherwise specifically limited, the term “polymer”shall include all possible geometrical configurations of the material.These configurations include, but are not limited to isotactic,syndiotactic and atactic symmetries.

[0028] “Spunbond fiber” refers to small diameter fibers which are formedby extruding molten thermoplastic material as filaments from a pluralityof fine capillaries of a spinnerette having a circular or otherconfiguration, with the diameter of the extruded filaments then beingrapidly reduced as by, for example, in U.S. Pat. No. 4,340,563 to Appelet al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No.3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and 3,341,394 toKinney, U.S. Pat. No. 3,502,763 to Hartmann, U.S. Pat. No. 3,502,538 toPetersen, and U.S. Pat. No. 3,542,615 to Dobo et al., each of which isincorporated herein in its entirety by reference. Spunbond fibers arequenched and generally not tacky when they are deposited onto acollecting surface. Spunbond fibers are generally continuous and oftenhave average deniers larger than about 0.3, more particularly, betweenabout 0.6 and 10.

[0029] “Wet pick-up” refers to the amount of a liquid absorbed by asubstrate. In particular, the wet pick-up is the amount of liquidabsorbed in relation to the dry weight of the substrate.

[0030] These terms may be defined with additional language in theremaining portions of the specification.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0031] The present invention is directed to a method that can be used totreat nonwoven materials, including high bulk and high basis weightnonwoven materials, with uniform coverage and treatment penetrationthroughout the web, without destroying the bulk or the structure of theweb. A target add-on level of the treatment, suitably between about 0.5%and about 4% weight by solids, can be achieved by balancing solutionconcentration, line speed, and vacuum air velocity.

[0032] The method of the invention can be carried out using theapparatus shown in FIG. 1. More particularly, a nonwoven web 20 can befed from an unwinder 22 into a treatment bath 24 having a controlledconcentration. The web 20 is not fed through any nip rolls or any othertype of pinch point but instead is submerged in the bath 24 and followsan unobstructed path below a rotor or bar 26 fixed within a container 28that holds the treatment bath 24. By dipping the web 20 in this manner,the web becomes fully saturated to provide uniform treatment andpenetration throughout the web.

[0033] The concentration of the treatment bath 24 is an important factorin controlling the add-on level of the treatment. To add hydrophilicityto a hydrophobic nonwoven web, the treatment bath suitably includes oneor more surfactants. One example of a commercially available surfactantis MASIL SF-19 silicone surfactant, available from BASF Corporation.Another example of a commercially available surfactant is AHCOVEL BaseN-62, available from Uniqema Inc., a division of ICI of New Castle, Del.The treatment bath may also include a dye, such as LEUCOPHOR B-302fluorescent brightener dye, available from Clariant of Muttenz,Switzerland, or other non-reactive additive. The concentration of thesurfactant(s) is suitably between about 0.2% and about 8%, or betweenabout 0.5% and about 4%, in an aqueous solution, depending on the finaladd-on level desired.

[0034] The add-on level can be determined by subtracting the dry weightof the untreated nonwoven web from the dry weight of the same nonwovenweb after being treated, then dividing the difference by the dry weightof the untreated nonwoven web. To achieve the target add-on level, thewet weight of the treated sample should be about double the dry weight.In other words, the nonwoven web should have about 100% wet pick-up ofthe treatment bath, or between about 25% and about 300%, or betweenabout 25% and about 200%, wet pick-up, depending on the nonwovendensity, fiber size, and shape. By having a wet pick-up of about 100%,the add-on level is roughly equal to the concentration of the treatmentbath. Alternatively, with a higher concentration solution, for exampledouble, then 50% pick-up would result in the same add-on level as the100% pickup. Less wet pick-up provides less water to drive off andtherefore more efficient drying.

[0035] The saturated nonwoven web 20 is fed from the treatment bath 24to a vacuum extraction device 30 that includes one or more vacuums 32.Each vacuum 32 extracts excess bath from the web 20. The air velocity ofthe vacuum 32 is another important factor in controlling the add-onlevel of the treatment. Air velocity depends on the vacuum slotdimensions, or surface area of the vacuum slot(s), as well as the volumeof air or air pressure pulled through the vacuum slot(s). Moreparticularly, air velocity of each vacuum is suitably between about 100and about 3000 feet per minute (fpm), or between about 1200 and about2000 fpm, for a 50 gsm fabric.

[0036] Unlike processes that use nip rolls to squeeze excess bath fromthe web, the use of a vacuum 32 to extract the excess bath from the webhas not shown any decrease in bulk. In fact, the bulk has actuallyincreased by about 10% in some cases as a result of undergoing thevacuum and subsequently being run through a dryer. By using one or morevacuums 32 in place of nip rolls, material can be passed through theexcess bath removal area without undergoing any contact between twosurfaces. This in turn prevents or reduces compression and shearingforces on the web. Furthermore, methods involving nip rolls aretypically limited to low bath concentrations. In contrast, higher bathconcentrations can be used in the present invention because vacuums canmore effectively extract excess bath compared to nip rolls withoutdamaging the web.

[0037] The vacuum extraction device 30 may also include one or morerotary valves 34 attached to, or within a vacuum line of, one or morevacuums 32. In general, a rotary valve is a flat circular plate havingintermittent holes such that when the rotary valve spins the vacuum ductis intermittently occluded and opened. Suitable rotary valves aretaught, for example, in U.S. Pat. No. 5,913,329 issued Jun. 22, 1999 toHaynes et al. The rotary valves 34 could be pulsed to perturb the vacuumsignal such that the vacuum strength goes up and down, thereby creatingzone treatment on the nonwoven web 20 such that areas of low and hightreatment levels are produced. More particularly, by pulsing the rotaryvalves 34, more or less treatment liquid is retained in the web 20 whenthe vacuum has less or more strength, respectively. Thus, the web 20could have areas of low and high treatment levels in cross directionalzones, or machine directional zones, or a combination of crossdirectional and machine directional zones. Arrow 36 indicates themachine direction of the process.

[0038] The nonwoven web 20 is then fed from the vacuum extraction device30 to a dryer 38 to evaporate any remaining water from the nonwoven web.The dryer 38 is suitably set at a temperature between about 200 andabout 250 degrees Fahrenheit.

[0039] A winder 40 pulls the nonwoven web 20 from the dryer 38 and, ifdesired, guides the dried web onto a spool or roll 42 for storage. Theunwinder 22 and the winder 40 control the movement of the nonwoven web20 from the treatment bath 24 to the vacuum or vacuums 32 and to thedryer 38, suitably at a line speed of between about 50 and about 200feet per minute, or up to about 2000 feet per minute, or even faster.The line speed is another important factor in controlling the add-onlevel of the treatment. In fact, a direct relationship exists betweenthe line speed and the vacuum level applied to the web. Morespecifically, if the line speed is increased, the vacuum level appliedto the web will be increased, and if the line speed is reduced, thevacuum level applied to the web will be reduced in order to maintain thesame add-on level. Thus, by balancing solution concentration, linespeed, and vacuum air velocity, a target add-on level of the treatmentcan be achieved.

[0040] Conventional drive means and other conventional devices which maybe utilized in conjunction with the apparatus of FIG. 1 are well knownand, for purposes of clarity, have not been illustrated in FIG. 1.

[0041] The method of the invention is particularly suitable for treatingnonwoven materials having high bulk and high basis weight. Morespecifically, the method may be used to treat nonwoven webs having athickness of at least 0.08 inches, or between about 0.1 and about 1.5inches, with a basis weight between about 34 and about 500 grams persquare meter. Nonwoven webs treated in accordance with the method of theinvention may be high-loft, open materials having a density of less thanabout 0.08 grams per cubic centimeter (g/cc), or less than about 0.06g/cc, or less than about 0.04 g/cc.

[0042] Nonwoven webs used in the method of the invention may be made offilament-forming polymers such as, for example, polyolefins, polyesters,polyamides, polycarbonates, polyurethanes, polyvinylchloride,polytetrafluoroethylene, polystyrene, polyethylene terephthalate,biodegradable polymers such as polylactic acid and copolymers and blendsthereof. Suitable polyolefins include polyethylene, e.g., high densitypolyethylene, medium density polyethylene, low density polyethylene andlinear low density polyethylene; polypropylene, e.g., isotacticpolypropylene, syndiotactic polypropylene, blends of isotacticpolypropylene and atactic polypropylene, and blends thereof;polybutylene, e.g., poly(1-butene) and poly(2-butene); polypentene,e.g., poly(1-pentene) and poly(2-pentene); poly(3-methyl-1-pentene);poly(4-methyl 1-pentene); and copolymers and blends thereof. Suitablecopolymers include random and block copolymers prepared from two or moredifferent unsaturated olefin monomers, such as ethylene/propylene andethylene/butylene copolymers. Suitable polyamides include nylon 6, nylon6/6, nylon 4/6, nylon 11, nylon 12, nylon 6/10, nylon 6/12, nylon 12/12,copolymers of caprolactam and alkylene oxide diamine, and the like, aswell as blends and copolymers thereof. Suitable polyesters includepolyethylene terephthalate, polytrimethylene terephthalate, polybutyleneterephthalate, polytetramethylene terephthalate,polycyclohexylene-1,4-dimethylene terephthalate, and isophthalatecopolymers thereof, as well as blends thereof.

[0043] The filaments may be monocomponent filaments, meaning filamentsprepared from one polymer component, multiconstituent filaments, ormulticomponent filaments. The multicomponent filaments may have eitherof an A/B or A/B/A side-by-side cross-sectional configuration, or asheath-core cross-sectional configuration, wherein one polymer componentsurrounds another polymer component. Furthermore, the filaments may bemeltblown fibers, spunbond fibers, or any other suitable type offilaments. Suitable types of nonwoven webs include spunbond webs,meltblown webs, and bonded carded webs. In one embodiment, the nonwovenweb may be a multi-layer material having, for example, at least onelayer of spunbonded web joined to at least one layer of meltblown web,bonded carded web or other suitable material.

[0044] Nonwoven webs treated in accordance with the method of theinvention are particularly suitable for use in disposable absorbentproducts including, without limitation, diapers, training pants,swimwear, absorbent underpants, adult incontinence products, femininehygiene products, absorbent wipes, and the like, as well as protectivegarments, including medical garments and industrial protective garments.Medical garments include surgical garments, gowns, aprons, face masks,absorbent drapes, and the like. Industrial protective garments includeprotective uniforms, workwear, and the like.

EXAMPLE

[0045] In this example, samples treated by four different treatmenttechniques, including the treatment technique of the invention, weretested and compared. Each of the samples included a high-loft,low-density web that was made with 3.7 denier bicomponent spunbond fiberat about 0.14 inches loft, about 100 gsm basis weight and 0.027 g/ccdensity prior to treatment.

[0046] Dip & Vacuum Treatment

[0047] The dip and vacuum treatment of the invention was carried outusing the apparatus shown in FIG. 1. A 1% solution of AHCOVEL Base N-62and SF-19 (2:1) was provided in a treatment bath. More specifically, thesolution included 200 grams AHCOVEL BASE N-62; 100 grams SF-19; 14,700grams water; and 1.5 grams LEUCOPHOR B-302 fluorescent brightener dye(optional). The nonwoven web had 100% wet pick-up to achieve the desired1% add-on level. The web was transported at a line speed of 50 feet perminute (fpm) to a 100 hp vacuum at 2 inches of water. The vacuum slothad dimensions of about 0.25 inch by 12 inches, with slot face airvelocity of about 1500 fpm. Subsequently, the web was transported to adryer having a temperature of about 240 degrees Fahrenheit. NMR testresults showed that the target add-on level was achieved.

[0048] The LEUCOPHOR B-302 fluorescent brightener dye was included inthe solution to determine the uniformity of coverage and thoroughness ofpenetration of the treatment. A 10-inch by 12-inch sample of the treatedmaterial was viewed under a black light. A photograph of a top view ofthe treated material under black light is shown in FIG. 2, and showssubstantially uniform coverage of the web.

[0049] Internal Treatment

[0050] Liquid MASIL SF-19 silicone surfactant, available from BASFCorporation, was injected directly into a polyethylene extruder barrelof a spunbonded forming apparatus. Add-on levels were targeted to 1% byweight on the web. To achieve this level, 2% SF-19 was added to thepolyethylene side of the fiber.

[0051] WEKO Treatment

[0052] Using low flow heads on a WEKO apparatus, a 15% solution ofAHCOVEL BASE N-62 and SF-19 (2:1) was applied to both sides of thenonwoven web. More specifically, the solution included 1500 gramsAHCOVEL BASE N-62; 750 grams SF-19; 12,750 grams water; and 11.25 gramsLEUCOPHOR B-302 fluorescent brightener dye (optional). The nonwoven webwas run through the WEKO at 25 feet per minute. With the 15% bath, toachieve an add-on of 1%, the web had a wet pick-up of 6.67%. To achievean add-on of 2%, the web had a wet pick-up of 13.33%.

[0053] The same results were obtained on a WEKO apparatus with high flowheads using a 7.5% solution of AHCOVEL BASE N-62 and SF-19 (2:1) appliedto both sides of the nonwoven web. More specifically, the 7.5% solutionincluded 750 grams AHCOVEL BASE N-62; 375 grams SF-19; 13,875 gramswater; and 5.6 grams LEUCOPHOR B-302 fluorescent brightener dye(optional).

[0054] The LEUCOPHOR B-302 fluorescent brightener dye was included inthe solution to determine the uniformity of coverage and thoroughness ofpenetration of the treatment. A 10-inch by 12-inch sample of the treatedmaterial was viewed under a black light. A photograph of a top view ofthe treated material under black light is shown in FIG. 3a, with across-sectional view of the material shown in FIG. 3b. As can be seen inthe photographs, particularly in FIG. 3b, only the surface appears to betreated, with very little penetration through the thickness of thesample.

[0055] Foam Treatment A 15% solution of AHCOVEL BASE N-62 and SF-19(2:1) was mixed with GLUCOPON foaming agent, available from Cognis.Corporation, Charlotte, N.C., (2:1):1 for the foaming process. The bathwas 1,000 grams, including 15% solids (150 grams total chemicals). Morespecifically, the bath included 3 parts AHCOVEL BASE N-62/SF-19 (112.5grams, including 75 grams AHCOVEL BASE N-62 and 37.5 grams SF-19) and 1part GLUCOPON (37.5 grams), with 850 grams water and 0.75 gram dye(optional). The bath can be converted to a 15,000 gram bath bymultiplying all values by 15.

[0056] Both sides of the nonwoven web were treated by mixing the bathand allowing the bath to blend for approximately 45 minutes, untilconsistent foam was produced. Then, the nonwoven web was run through afoaming apparatus at a line speed of 60 fpm for 2% add-on, or at 120 fpmfor 1% add-on, pulling the web over a foam slot. The flow of the foamwas 22 cubic centimeters per minute, with air flow of 5 liters perminute. The foamer was set at a speed of 500 rpm, temperature of 94degrees Fahrenheit, and pressure of 25 psi. A through-air dryer was setat 240 degrees Fahrenheit.

[0057] The LEUCOPHOR B-302 fluorescent brightener dye was included inthe solution to determine the uniformity of coverage and thoroughness ofpenetration of the treatment. A 10-inch by 12-inch sample of the treatedmaterial was viewed under a black light. A photograph of a top view ofthe treated material under black light is shown in FIG. 4a, with across-sectional view of the material shown in FIG. 4b. As can be seen inboth the treatment application was non-uniform on the surface as well asthrough the thickness of the web.

[0058] FIFE Test

[0059] A horizontal Fluid-Intake and Flowback Evaluation (FIFE) Test wasperformed on each of the four types of treated samples described above.This test determines the intake potential, or the time it takes for eachsample to absorb fluid and the amount of fluid that flows back out ofthe sample after fluid has been absorbed.

[0060] The FIFE entails insulting the structure by pouring a definedamount of 0.9 percent saline solution into a cylindrical column restingvertically on top of the structure and recording the time it takes forthe fluid to be taken in by the structure. The sample to be tested isplaced on a flat surface and the FIFE testing apparatus placed on top ofthe sample. The FIFE testing apparatus consisted of a rectangular, 35.3by 20.3 cm, plexiglass piece upon which was centered a cylinder with aninside diameter of 30 mm. The flat piece had a 38 mm hole correspondingwith the cylinder so that fluid could pass through it from the cylinderto the sample. The cylinder was centered 2 inches from top or front ofthe absorbent pad in the crotch of diaper. The FIFE testing apparatusweighed 517 grams.

[0061] Intake times are typically recorded in seconds. Samples were cutinto 2.5 by 7 inch pledgets and were inserted into a STEP 4 HUGGIESULTRATRIM® commercially available diaper after removing the surgemanagement layer from the diaper, thereby replacing the surge managementlayer with a sample pledget. The diapers including the samples were theninsulted three times at 100 ml per insult with a wait of 15 minutesbetween the time the fluid was completely absorbed and the next insult.

[0062] After the third insult, the materials were placed on a vacuum boxunder 0.5 psi of pressure with a piece of blotter paper on top. Theblotter paper was 110 lb. Verigood paper made by Fort James Corporationand was 3.5 by 12 inches (8.9 by 30.5 cm). The blotter paper was weighedbefore and after the test and the resulting differential reported as theflowback value as grams of fluid desorbed.

[0063] The results of the FIFE test are shown in FIG. 5.

[0064] LISTER Test

[0065] A LISTER type timer/dispenser, manufactured by LenzingAktiengesellschaft, Division Lenzing Technik, A-4860 Lenzing, Austria,was used to determine the time it takes for each sample to absorb orintake cumulative amounts of fluid. More specifically, 4-inch by 4-inchtreated samples were placed over 2 plies of control Lister absorbentpaper. Then 10 ml of saline was applied to each 4-inch by 4-inch sampleusing the Lister apparatus. The apparatus measures the time in secondsfor the saline to pass into the samples. The time is then recorded, andthe absorbent papers that have soaked up the saline that has passedthrough the samples are discarded. Samples are blotted dry using papertowels. The, test is repeated 9 additional times, drying samples betweeninsults and using new absorbent paper for each insult. The results ofthe LISTER test for the WEKO sample, the dip & vacuum sample of theinvention, the foam sample, and a control treated bonded carded web (at100 gsm) are shown in FIG. 6. The bonded carded web (BCW) was producedfrom a 300 gsm web made up of a mixture of 2 denier T-256 bicomponentfibers and 3 denier T-244 polyester fibers at a ratio of 60/40,respectively. Both fibers are commercially available from KoSa Inc. Thefibers were treated by the manufacturer with 0.5 weight percent of aproprietary surfactant to make them hydrophilic.

[0066] While in the foregoing specification this invention has beendescribed in relation to certain preferred embodiments thereof, and manydetails have been set forth for purpose of illustration, it will beapparent to those skilled in the art that the invention is susceptibleto additional embodiments and that certain of the details describedherein can be varied considerably without departing from the basicprinciples of the invention.

What is claimed is:
 1. A method of treating a nonwoven web, comprising:saturating the nonwoven web in a treatment bath having a concentrationbetween about 0.2% and about 8%; using at least one vacuum to extractexcess bath from the nonwoven web; and using a dryer to evaporate waterfrom the nonwoven web.
 2. The method of claim 1, wherein the treatmentbath comprises at least one surfactant in an aqueous solution.
 3. Themethod of claim 2, wherein the treatment bath further comprises a dye.4. The method of claim 2, wherein the treatment bath comprises betweenabout 0.2% and about 8% of the at least one surfactant in the aqueoussolution.
 5. The method of claim 2, wherein the treatment bath comprisesbetween about 0.5% and about 4% of the at least one surfactant in theaqueous solution.
 6. The method of claim 1, further comprisingtransporting the nonwoven web from the treatment bath to the at leastone vacuum at a line speed up to 2000 feet per minute.
 7. The method ofclaim 1, further comprising transporting the nonwoven web from thetreatment bath to the at least one vacuum at a line speed between about50 and about 200 feet per minute.
 8. The method of claim 1, furthercomprising using the at least one vacuum to control the percent add-onlevel to between about 0.5% and about 4% weight by solids.
 9. The methodof claim 1, wherein the at least one vacuum has an air velocity betweenabout 100 and about 3000 feet per minute.
 10. The method of claim 1,comprising using a plurality of vacuums to extract excess bath from thenonwoven web.
 11. The method of claim 1, further comprising pulsing theat least one vacuum to create zone treatment.
 12. The method of claim11, wherein the zone treatment is in one of a cross direction, a machinedirection, and a combination thereof.
 13. The method of claim 1, whereinthe dryer is set at a temperature between about 200 and about 250degrees Fahrenheit.
 14. The method of claim 1, further comprisingwinding the nonwoven web onto a spool.
 15. The method of claim 1,wherein the nonwoven web has between about 25% and about 300% wetpick-up of the treatment bath.
 16. The method of claim 1, wherein thenonwoven web has a thickness of at least 0.08 inches.
 17. The method ofclaim 1, wherein the nonwoven web has a thickness of between about 0.1and about 1.5 inches.
 18. The method of claim 1, wherein the nonwovenweb has a basis weight between about 34 and about 500 grams per squaremeter.
 19. The method of claim 1, wherein the nonwoven web has a densityof less than about 0.08 grams per cubic centimeter.
 20. The method ofclaim 1, wherein the nonwoven web has a density of less than about 0.06grams per cubic centimeter.
 21. The method of claim 1, wherein thenonwoven web has a density of less than about 0.04 grams per cubiccentimeter.
 22. A method of treating a hydrophobic nonwoven web,comprising: saturating the nonwoven web in a treatment bath including atleast one surfactant in an aqueous solution at a concentration betweenabout 0.2% and about 8%; using at least one vacuum to extract excessbath from the nonwoven web and to control percent add-on level of thetreatment to between about 0.5% and about 4% weight by solids; using adryer to evaporate water from the nonwoven web.
 23. The method of claim22, wherein the treatment bath comprises between about 0.5% and about 4%of the at least one surfactant in the aqueous solution.
 24. The methodof claim 22, wherein the treatment bath further comprises a dye.
 25. Themethod of claim 22, further comprising transporting the nonwoven webfrom the treatment bath to the at least one vacuum at a line speed up toabout 2000 feet per minute.
 26. The method of claim 22, furthercomprising transporting the nonwoven web from the treatment bath to theat least one vacuum at a line speed between about 50 and about 200 feetper minute.
 27. The method of claim 22, wherein the at least one vacuumhas an air velocity between about 100 and about 3000 feet per minute.28. The method of claim 22, comprising using a plurality of vacuums toextract excess bath from the nonwoven web.
 29. The method of claim 22,further comprising pulsing the at least one vacuum to create zonetreatment.
 30. The method of claim 29, wherein the zone treatment is inone of a cross direction, a machine direction, and a combinationthereof.
 31. The method of claim 22, wherein the dryer is set at atemperature between about 200 and about 250 degrees Fahrenheit.
 32. Themethod of claim 22, further comprising winding the nonwoven web onto aspool.
 33. The method of claim 22, wherein the nonwoven web has betweenabout 25% and about 300% wet pick-up of the treatment bath.
 34. Themethod of claim 22, wherein the nonwoven web has a thickness of at least0.08 inches.
 35. The method of claim 22, wherein the nonwoven web has athickness of between about 0.1 and about 1.5 inches.
 36. The method ofclaim 22, wherein the nonwoven web has a basis weight between about 34and about 500 grams per square meter.
 37. The method of claim 22,wherein the nonwoven web has a density of less than about 0.08 grams percubic centimeter.
 38. The method of claim 22, wherein the nonwoven webhas a density of less than about 0.06 grams per cubic centimeter. 39.The method of claim 22, wherein the nonwoven web has a density of lessthan about 0.04 grams per cubic centimeter.
 40. Apparatus for treating anonwoven web, comprising: a treatment bath having a concentrationbetween about 0.2% and about 8%; at least one vacuum; a dryer; a devicefor transporting the nonwoven web from the treatment bath to the atleast one vacuum to the dryer.
 41. The apparatus of claim 40, whereinthe treatment bath comprises at least one surfactant in an aqueoussolution.
 42. The apparatus of claim 41, wherein the treatment bathfurther comprises a dye.
 43. The apparatus of claim 41, wherein thetreatment bath comprises between about 0.2% and about 8% of the at leastone surfactant in the aqueous solution.
 44. The apparatus of claim 41,wherein the treatment bath comprises between about 0.5% and about 4% ofthe at least one surfactant in the aqueous solution.
 45. The apparatusof claim 40, wherein the at least one vacuum has an air velocity betweenabout 100 and about 3000 feet per minute.
 46. The apparatus of claim 40,further comprising at least one rotary valve attached to the at leastone vacuum.
 47. The apparatus of claim 40, comprising a plurality ofvacuums.
 48. The apparatus of claim 40, wherein the dryer is set at atemperature between about 200 and about 250 degrees Fahrenheit.
 49. Theapparatus of claim 40, wherein the device for transporting the nonwovenweb from the treatment bath to the at least one vacuum to the dryer hasa line speed up to about 2000 feet per minute.
 50. The apparatus ofclaim 40, wherein the device for transporting the nonwoven web from thetreatment bath to the at least one vacuum to the dryer has a line speedbetween about 50 and about 200 feet per minute.
 51. The apparatus ofclaim 40, further comprising a spool onto which the nonwoven web can bewound.